Our objective is to clarify the role of polyoma T antigens in cell transformation. We will isolate mutants affecting the medium T antigen of polyoma. We will construct recombinant DNA's to allow the T antigens to be synthesized in bacteria, or in high amounts in mammalian cells. We will study functions associated witht the T antigens, particularly a protein kinase activity of unusual specificity in polyoma T antigen immunoprecipitates. We will seek to relate T antigen functions to mechanisms of cell growth control by studying the control of transcription in polyoma infected and transformed cells, and early viral functions such as mitogenic activity and events leading to anchorage-independent growth.